FT8 Operating Guide
6
7
. Click OK and OK again to exit the Windows sound settings.
2
. Launch WSJT-X if it is not already running . With your
Clap your hands or shout out: if
you see the bar graph level flick
up, you may have selected the
PC’s microphone rather than the
radio input! Oops. Easily done.
radio OFF, check the bar graph at the bottom left corner
of WSJT-X main screen. The level should be at or near
zero, flickering red. There may be a few dBs of noise
generated in your sound card, or a little stray pickup on
its input (e.g. some AC hum if it is poorly shielded). If
you see a lot of input, something is wrong. Check that you have selected the radio audio input
to WSJT-X under F2 Settings Audio. The input should show the sound card line or
microphone input from the radio that you checked/adjusted above.
8
. Now turn ON your radio and tune to a quiet
In contrast to VHF/UHF, there are
band, with the attenuator off, RF gain up high
usually lots of strong FT8 signals on the
HF bands at peak times: “weak” HF DX
signals are generally only weak relative
to other HF signals, rather than weak in
absolute terms relative to the noise
floor, so strong signal handling and
and preamp set as normal. You should hear just
a little background noise on the radio - band
noise plus noise generated in the receiver
itself. The bar graph in WSJT-X should be read
about 30 dB. You may need to adjust the audio
output level from the radio (the Line Out level if
dynamic range tends to be more
you have that facility, otherwise the AF level) and
important than sensitivity on HF.
until WSJT-X shows about 30 dB.
9
. If your radio has a fixed (non-adjustable) line level output or one
It might be worth
comparing different
USB ports for your
USB sound system or
that cannot be reduced to about 30 dB on a dead band, have you
plugged the radio line output into the microphone socket on the
PC sound card by mistake? Or have you selected the microphone
input rather than the line input on the sound card? Check the
labels on the sound card inputs and the sound card settings. If
there is no “line in” but only a “microphone” input, and no way to
turn off the microphone preamplifier in the sound card settings,
you might need an external attenuator (e.g. a potentiometer) in
rig connection: some
are noisier than
others in my
experience.
the audio lead from your radio to reduce the audio level feeding
into your PC sound card, or you may need to use the radio’s headphone output rather than
the line out, using the radio’s AF gain control to set the quiescent level on the WSJT-X bar
graph to (yes, you guessed it) about 30 dB.
1
0. Now tune to band that has some life in it, using
If there is so much band activity that
the band selector on the WSJT-X main
the bar graph is near the top of the
screen. You should hear FT8 signals on the radio
scale and turning red, turn off the
and see signal blobs on the waterfall. The WSJT-
radio’s preamp, turn on the attenuator
3
X bar graph should read about 40 to 70 dB , still
and/or reduce the RF gain to bring the
in the green, and after a period or two you should
levels back down to the green zone.
see some decodes appear.
That’s it, you’re done! To avoid having to repeat this whole process, you might like to make some
notes about the settings though, just in case ‘someone’ fiddles with ‘something’.
2
If your radio has a built-in sound card and USB interface, you won’t be able to use the sound card while the radio is switched
off … but to simulate no audio input, maybe you can tune to a dead band and disconnect your antenna? [Tnx tip VE3AND]
3
The dB values here are decibels relative to a reference level, the digitized signal value 0001.
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